Biomedical subjects

J Vachek

Publications and source records attributed to J Vachek.

At least 19 recordsLinked to original sources

PubMed2004

Biochemical effects of low level exposure to soman vapour.

The aim of this study was to demonstrate changes in acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities, tyrosine aminotransferase activity (TAT) and plasma corticosterone level, neuroexcitability and behavior following 24 hours and 4 weeks of soman sublethal inhalation exposure at low level. AChE activity in erythrocytes and BuChE activity in plasma was decreased (dependent on the concentration of soman) 24 h and 4 weeks after the exposure. Similar decrease in AChE activity in different brain parts was observed. One of stressogenic parameters (TAT) was changed after 24 h exposure only. 4 weeks after the exposure, these parameters (corticosterone and TAT) were in the range of normal values. Behaviour of experimental animals was changed 24 h after the exposure persisting 4 weeks after the exposure as well as neuroexcitability.

Acetylcholinesterase↗

PubMed2002

A comparison of the efficacy of pyridostigmine alone and the combination of pyridostigmine with anticholinergic drugs as pharmacological pretreatment of tabun-poisoned rats and mice.

The ability of two types of pharmacological pretreatment (pyridostigmine alone or pyridostigmine in combination with two anticholinergic drugs) to increase the resistance of rats and mice against tabun and to increase the therapeutic efficacy of common antidotal treatment of tabun-poisoned rats and mice was compared. A significant decrease in the LD50 values of tabun was observed when mice as well as rats were pretreated with the prophylactic antidotal mixture consisting of pyridostigmine, benactyzine and trihexyphenidyle, designated PANPAL. Pyridostigmine-pretreated rats were also more resistant against acute lethal effects of tabun but pyridostigmine-induced resistance of rats was not so high as PANPAL-induced resistance. In addition, the pharmacological pretreatment with pyridostigmine alone was not able to protect mice against tabun-induced acute toxicity. The pharmacological pretreatment with pyridostigmine alone was able to increase the efficacy of currently used antidotal treatment (obidoxime in combination with atropine and diazepam) of tabun-induced poisoning, but PANPAL-induced increase in the efficacy of the same antidotal treatment was significantly higher than an increase induced by pyridostigmine alone. PANPAL-induced increase in the efficacy of antidotal treatment of tabun poisoning was also observed in mice. These findings confirm that PANPAL pretreatment of tabun-poisoned rats and mice seems to be much more suitable than currently used pyridostigmine alone.

Animals↗

PubMed2001

The influence of low-level sarin inhalation exposure on spatial memory in rats.

To study the influence of low-level sarin exposure on cognitive functions, the rats were exposed to three various low concentrations of sarin (Levels 1-3) for 60 min in the inhalation chamber. In addition, one group of rats was exposed to Level 2 of sarin repeatedly. Testing of cognitive functions was carried out using the Y-maze evaluating learning and spatial memory. The correct averse behavior of sarin-exposed rats in the Y-maze was tested several times within 6 weeks following sarin inhalation exposure to look for any cognitive impairments. The results were compared to the Y-maze performance of control rats exposed to pure air instead of sarin. While a subtle and short-term deficiency in the Y-maze performance was observed in rats exposed to the Levels 1 and 2 of sarin, the exposure to the Level 3 of sarin caused a significant decrease in the Y-maze performance for a relatively long time. Similar sarin-induced spatial memory impairments were demonstrated in rats exposed repeatedly to the Level 2. A decrease in the Y-maze performance was observed until the end of the third week following the last exposure to sarin. Thus, our findings confirm that both nonconvulsive symptomatic and clinically asymptomatic concentrations of sarin can cause relatively long-term memory impairments in sarin-poisoned rats when the rats are exposed to clinically asymptomatic sarin concentration repeatedly.

Administration, Inhalation↗

PubMed2001

The long-term influence of low-level sarin exposure on behavioral and neurophysiological functions in rats.

1. Long term effects of low doses of highly toxic organophosphorus agent sarin on behavioral and neurophysiological functions were studied in rats exposed to sarin by inhalation. The toxic effects of sarin were monitored using a functional observational battery (FOB), an automatic measurement of motor activity and a test of excitability of central nervous system at 3, 6 and 12 months following sarin exposure. 2. The results indicate that sarin at symptomatic as well as asymptomatic doses (level 2 and 3) is able to induce some neurotoxic effects (a decrease in activity and mobility, an alteration of gait, an increase in stereotyped behavior) including an increase in the excitability of central nervous system (an increase in convulsive activity following the administration of pentamethylenetetrazole) in rats at 3 months following inhalation exposure. Some sings of increased excitability were also observed in sarin-exposed rats following 6 or 12 months (an increase in exploratory activity, body temperature and a hindlimb grip strength at 6 months following exposure to sarin at asymptomatic doses, an increase in tail-pinch response at 12 months following exposure to sarin at symptomatic doses). 3. Therefore, nerve agents such as sarin seem to be harmful not only at high, clinically symptomatic doses but also at low, clinically asymptomatic doses because of long term manifestation of alteration of neurophysiological functions in sarin-exposed rats without disruption of cholinergic nervous system.

Animals↗

PubMed2001

Long-term effects of low-level sarin inhalation exposure on the spatial memory of rats in a T-maze.

1. To study the influence of low-level sarin exposure on cognitive functions, male albino Wistar rats were exposed to three various low concentrations of sarin (LEVEL 1-3) for 60 minutes in the inhalation chamber. Testing of cognitive functions was carried out using the T-maze evaluating learning and spatial memory. The behavior of sarin-exposed rats in the T-maze was tested several times within five weeks following sarin inhalation exposure to look for any cognitive impairments. The alteration of cognition was evaluated by using a method studying memory elicitation in response to appetitive motivation in a multiple T-maze. 2. Statistically significant, short-term deficiency in the T-maze performance was observed in rats exposed to symptomatic (LEVEL 3) as well as clinically asymptomatic concentration (LEVEL 2) of sarin. The repeated exposure of rats to clinically asymptomatic dose of sarin (LEVEL 2R) did not change the effect of low-level sarin exposure on spatial memory compared to the single exposure to the same dose of sarin. 3. Thus, sarin is able to influence the cognitive functions (e.g. spatial memory) even at low doses that do not cause clinically manifested intoxication following the inhalation exposure. Nevetheless, the alteration of spatial memory lasts for a short time only, in contrast with the severe sarin poisoning.

Administration, Inhalation↗

PubMed2000

The long-term changes in liver DNA and total protein contents following low level sarin exposure in rats.

1. The changes in contents of DNA and total protein in the liver of the rats exposed to low level sarin by inhalation at 3, 6 and 12 months following the exposure were studied. The influence of sarin on the DNA and protein metabolism in liver was determined by the measurements of incorporation of tritiated thymidine into DNA, the concentration of DNA and total protein. 2. Our results show that not only symptomatic level 3 but also asymptomatic levels 1 and 2 of sarin are able to significantly decrease the incorporation of radiolabelled thymidine without changing total concentrations of DNA as well as protein at three months following sarin exposure. On the other hand, the significant decrease in total contents of DNA and protein in liver without the changes in the incorporation of tritiated thymidine was determined in liver six months following sarin exposure. Practically no significant changes in the metabolism of DNA and protein were observed at 12 months following sarin exposure. 3. Thus, not only clinically manifested intoxication but also low-level, asymptomatic exposure to nerve agents such as sarin is able to influence the metabolism of nucleic acids as well as proteins even several months following the exposure.

Animals↗

PubMed2000

Long-term alteration of immune functions following low level exposure to sarin in rats.

1. Long term alteration of immune functions caused by low doses of nerve agent sarin were studied in rats exposed to sarin by inhalation. The alteration of immune functions by sarin was monitored by using two methods (the evaluation of in vitro spontaneous as well as stimulated proliferation of spleen cells and in vitro bactericidal activity of peritoneal macrophages) at 3, 6 and 12 months following sarin exposure. 2. The results indicate that not only symptomatic but also asymptomatic dose of sarin is able to alter some immune functions at six and twelve months following exposure to sarin. 3. Thus, not only organophosphorus insecticides but also nerve agents such as sarin can be potentially immunotoxic even at very low doses that do not cause clinically manifested intoxication following the inhalation exposure. The ability of sarin at low doses to alter immune functions seems to be really long term (up to 12 months following the exposure).

Administration, Inhalation↗

PubMed1997

[The effect of parasympatholytics on the therapeutic effectiveness of the oxime HI-6 against organophosphorus compounds (Soman, substance VX, Fosdrin) in mice].

BACKGROUND: Causal antidotal therapy of acute intoxications with organophosphorus compounds involving administration of the parasympatholytic and cholineesterase reactivator (oxime) has not been resolved so far satisfactorily despite knowledge of the basic mechanism of action of these noxious substances. METHODS AND RESULTS: In experiments on mice the therapeutic effect of parasympatholytics atropine, benactyzine and biperidene (Akineton) combined with oxime HI-6 on the toxicity of highly toxic organophosphates soman and substance VX and the organophosphorus insecticide phosdrine was compared as regards their influence on the LD50 of these noxious substances during 24-hour survival of experimental animals. Two levels of antidotes were tested. These findings confirm that the LD50 value of untreated intoxication with all three organophosphorus compounds is most increased by oxime HI-6 combined with benactyzine regardless of the antidote dosage. CONCLUSIONS: Oxime HI-6 is the most effective against highly toxic organophosphates and organophosphorus insecticides when combined with the centrally acting parasympatholytic benactyzine.

Animals↗

PubMed1996

Toxicities of O-alkyl S-(2-dialkylaminoethyl) methyl phosphonothiolates (V-compounds).

Toxicities expressed as LD50 values of O-alkyl S-(2-dialkylaminoethyl) methyl phosphonothiolates in different species and different routes of administration were determined. Rats were more sensitive to these compounds than mice, rabbits and guinea-pigs were more sensitive than mice and rats. The most sensitive to these compounds were dogs. LD50 values varied in a wide range, however, a decrease of toxicity was observed in the following rank: i.v., i.m., s.c., i.p., p.o. and p.c., respectively. Depending on the route of administration, LD50 values varied from 5 g/kg (i.m., dogs) through tens of microgram/kg for the most part of compounds and routes of administration to hundreds, rarely thousands of g/kg (some chemicals, p.c. administration).

Animals↗

PubMed1992

Acute toxicities of 2-dialkylaminoalkyl-(dialkylamido)-fluoro-phosphates.

Toxicities expressed as LD50 values of 2-dialkylaminoalkyl-(dialkylamido)-fluorophosphates for rats and mice (i.m. administration) were determined. Rats were more sensitive to these compounds than mice: LD50 values varied from 17 (rats) to 1222 (mice) micrograms/kg. LD50 values at different routes of administration (i.v., i.m., s.c., p.o. and p.c.) for one derivative of this group, 2-dimethylaminoethyl-(dimethylamido)-fluorophosphate, were determined. Depending on the route of administration, LD50 values varied from 11 (i.v.) to 190 (p.o.) micrograms/kg for rats and from 27.6 (i.v.) to 222 (p.o.) micrograms/kg for mice, respectively. Percutaneous toxicity in rats only (LD50 = 1366 micrograms/kg) was determined.

Animals↗

PubMed1992

2-Dialkylaminoalkyl-(dialkylamido)-fluorophosphates: acute toxicities.

Toxicities expressed as LD50 values of 2-dialkylaminoalkyl-(dialkylamid) o-fluorophophates for rats and mice (i. m. administration) were determined. Rats were more sensitive to these compounds than mice: LD50 values varied from 17 to 261 micrograms/kg for rats and from 30.5 to 1222 micrograms/kg for mice, respectively. Different routes of administration in one derivative of this group substituted by methyl groups only were compared. The highest toxicity (lowest LD50 value) in intravenous administration (11 micrograms/kg) and the lowest one in percutaneous (1366 micrograms/kg) were found.

Animals↗

PubMed1991

Pharmacokinetics and tolerance of 7-methoxytacrine following the single dose administration in healthy volunteers.

7-methoxy-tetrahydroaminoacridine (7-MEOTA) is a new reversible cholinesterase inhibitor. Forty-eight young male volunteers divided into six dosage groups were included into a single-dose pharmacokinetic study with either oral (p.o.) or intramuscular (i.m.) administration. The dose of 7-MEOTA was 2, 4 or 8 mg/kg body weight p.o. or 0.5, 1 or 2 mg/kg body weight i.m. in the respective six dosage groups. The plasma levels data were fitted to an open one-compartmental model. The compound showed cholinomimetic adverse effects in 2 subjects with the blood levels exceeding 1,500 micrograms/l. The red blood cells levels paralleled those in plasma and were 2.5 times higher. The tmax was 4 hours and 1 h, t1/2 8.7 +/- 3.9 hours and 6.5 +/- 5.8 hours in case of p.o. and i.m. administration, respectively. The apparent clearance (D/AUC) was 5 times higher following p.o. administration, reflecting the differences in bioavailability.

Administration, Oral↗

PubMed1987